Nowadays, many users experience usability issues with their electronic products. It does not work as they expect or otherwise irritates the user, so he becomes dissatisfied about the product and may even complain about it. Th ese numbers of complaints to companies and usability issues are high and rising. Reasons for these increasing numbers are the highly complex electronic products that are being developed, the global economy in which they are created and produced, and the wide variety of users that uses the product. It is highly challenging to develop these increasingly complex products and interactions and for the wide variety of users. So design for usability is becoming ever more important. Many usability techniques are available to create these products, however the pressure from the market results in limited time to develop usable products. Th is makes that feedback from the market is not available on time, that usability tests are skipped, and hasty decisions are made. This all, may lead to ‘incorrect’ decisions and consequently to usability issues. These are some of the aspects that complicate creating products and make that usability issues still occur, despite the available usability techniques. In design practice decision-making was investigated to find out what makes usability related decisionmaking ‘go wrong’. This was in order to improve decisionmaking and thereby reduce the number of usability issues. The research started with a literature study to clarify terms such as design and decision-making. Designing products is an iterative process to create products of which problem solving and finding creative solutions are part of. Within this process the designer encounters different kinds of problems; structured problems and ill-structured problems. Each of these problems requires different approaches; Rational Problem Solving for structured problems and Reflective Practice for ill-structured problems. Both approaches are used in the process of creating products. In design theory only limited literature on decision-making is available, therefore it was required to study decision-making in fields beyond design. Naturalistic Decision Making (NDM) literature appeared to be an interesting perspective on decision-making, possibly relevant to design. NDM researchers observed decision-making in the ‘real world’, outside the laboratories. They realised that Rational Problem Solving is not always possible in the ‘real world’ as decisionmakers have also to cope with ill-structured problems and other influencing factors and elements. NDM researchers identified two factors that influence decisionmaking; the ‘real world context’ and ‘uncertainty’. These factors infl uence the decision task, making it more difficult to make decisions, and aff ecting the quality of decisions possibly resulting in ‘incorrect’ decisions. The factor ‘real world context’ is characterised by various elements, for example, time pressure, iterative design and multiple stakeholders. The influencing factor ‘uncertainty’ is defined by the types what the decision-maker can be uncertain of and by the sources that induce uncertainty. Comparing these infl uencing factors from NDM theory with design theory showed a similarity between the elements that characterise the context and the aspects of uncertainty. This suggested that these infl uencing factors could also be relevant to decision-making in design. Therefore the NDM perspective was used to investigate usability related decision-making in design practice. Knowing what infl uences decision-making indicates how decision-making could be improved in order to reduce the number of usability issues. A first explorative study (Study 1) at a Dutch design agency was conducted to identify possible infl uencing factors on usability related decision-making. Th e results of eight retrospective interviews revealed three influencing factors on usability related decision-making: ¿ design context ¿ uncertainty ¿ unawareness The third influencing factor, which was not mentioned in literature, might be a critical factor as it could lead to unexpected surprises such as usability issues. Further investigation of this factor was required to verify whether unawareness actually is an influencing factor on usability related decision-making in design practice and whether it is critical or not. A second study (Study 2) was conducted at a multinational product development company. At that time unawareness was still an undefined term. In order to identify unawareness the consequences of this influencing factor were investigated; unforeseen usability issues. This was done by conducting retrospective interviews with 14 key team members, which revealed various unforeseen usability issues. Tracing them back, it could be concluded that unawareness plays a role during decision-making in design practice and that it is a critical influencing factor as various unforeseen usability issues resulted from it. These critical and unknown influencing factor required further investigation. The third study (Study 3) was a retrospective study at a multinational development company to obtain a better understanding of the influencing factor ‘unawareness’. The results were based on a document analysis of 2.056 project documents. Th is study provided detailed examples of unawareness during decision-making that resulted in unforeseen usability issues. A description of unawareness was made based on these various examples of unawareness in design practice. Unawareness is described – similar to uncertainty – by its types and sources. Three types of unawareness were identified to describe what the decision-maker can be unaware of: ¿ unawareness about information ¿ unawareness about the consequences ¿ unawareness about decisions Three sources were identifi ed that contribute to unawareness: ¿ inadequate consideration ¿ inadequate overview ¿ fixation In design practice, it is this influencing factor ‘unawareness’ that contributes to usability related decision-making going ‘wrong’. Th is in spite of the many available usability techniques, these techniques do not address the sources of unawareness. Unawareness during the decision-making process results in decisions of poor quality, leading to ‘incorrect’ decisions and usability issues. Therefore unawareness in the design process needs to be reduced to improve the quality of usability related decisions. To do so, it is necessary to acknowledge this influencing factor, recognise the sources of the factor and address the sources that induce the unawareness
